Brazilian forward Antony stepped off the bench to send Manchester United through to the Europa League last 16 as the hosts came from behind to beat Barcelona 2-1 in Thursday's playoff second leg and progress 4-3 on aggregate.
After a frantic start, Barca were awarded an 18th-minute penalty when Bruno Fernandes was adjudged to have fouled defender Alejandro Balde and Robert Lewandowski just squeezed the spot-kick home.
United came out for the second half looking like a different side and levelled through Fred, the Brazilian steering home Fernandes's pass two minutes after the break.
A superb save from goalkeeper David de Gea kept out an effort from Barca's Jules Kounde, a stop that proved crucial as Antony arrowed a superb finish into the bottom corner 17 minutes from time to send United through.
United remain in four competitions this season as they bid to win their first major trophy since 2017.
"The belief of the team is always there," Fernandes told BT Sport. "The belief of the fans, they push us through difficult moments.
"We have made great comebacks, the club is made also by that. In the past we have done a lot like this result."
{{/usCountry}}"We have made great comebacks, the club is made also by that. In the past we have done a lot like this result."
{{/usCountry}}Both sides have improved a great deal under their new coaches this season, with some of the football in the first leg testament to that and setting the tie up nicely for the return fixture under the lights at Old Trafford.
FERNANDES DENIED
United started well with captain Fernandes denied by a superb Marc-Andre ter Stegen save after being picked out by Casemiro.
Then came the moment that had Old Trafford united in incredulity as referee Clement Turpin pointed to the spot, a decision Fernandes could not believe. De Gea got a hand to Lewandowski's penalty, but could not claw it out.
The Polish striker has now scored 25 goals in 30 appearances across all competitions for the LaLiga leaders this season, the 12th successive campaign in which he has netted 25 or more goals at club level.
United did not create a chance of note for the remainder of the first half but whatever coach Erik ten Hag said at the break had an immediate effect as Fernandes found Fred to level.
The save from De Gea to tip Kounde's header over was world class and the finish from Antony also right out of the top drawer.
Substitutes have made a huge difference for United this term, with 19 goals scored by replacements in all competitions, the most of any big-five European league side in 2022-23.
The hosts survived nervy late moments, but saw out a first win over Barca since 2008 -- 1-0 in the second leg of the 2007-08 Champions League semi-final -- to end a five-game winless run against the Spanish side.
"United were very intense in that second half," Barca coach Xavi Hernandez said. "They are in very good form at the moment and are very good at home. It is those fine details that made all the difference.
"If Pedri or Gavi had been there today, maybe it would have been different in the second half."